Process and apparatus for making gut strings



Nov. 16, 19x13.A C. G. BJORKMAN 2,334,170

PROCESS AND APPARATUS FOR MAKING GUT STRING Filed March 20, 1941 3 Sheets-Sheet l A M m 1i i iiilullmwl;

Nov. 16, 1943.

C. G. BJORKMAN PROCESS AND APPARATUSTOR MAKING GUT STRING 3 Sheets-Sheet 2 QL/@ruhr Filed March 20, 1941 NOV w 1943 c. G. BJORKMAN NG GUT STRING PROCESS ANDl APPARATUS FOR MAKI 5 Sheets-Sheet 3 Filed March 20, 1941 ATTORNEYS.

Patented Nov. 16, 1943 recense AND APPARATUS non GU'i` STRINGS MAKING can G. Bjdrkmanycmagmiii. u Application/March 20, 1941,. SeriaLNo. 384,369. 01- ti-L-Sw 2 5 Claims.

In making gut stringsfor music strings, tennis rackets, surgical use,'or other purposes, it is very desirable to have the string of uniform cross section along its entire length, and to have it round in shape, compactin cross section and smooth surfaced. A gut stringisusually made by twisting a skein made up ofa.` few fine' ribbons cut from membrane. `In my prior Patent No. 2,104,730, I disclosed a methodoftwisting such strings by suspending them in water during the twisting operation, whichgreatly improved the vention is mainly designed as animprovement of the apparatus and methodofthisprior patent,

y although it may no doubtV be usedwithout the features of the'prior patent rifsuch use should, for any reason, be desired. A1 The present invention includes the subject matter'of 4my copending application Serial No. 302,063, led October 30,

1939, together with improvements thereon, andthis application is therefore=amcontinuation in part of said coperiding. application. i

In its more basic aspects, the presentinvention comprises the step of and means for. molding the string as it is being twisted. Since the twisting takes place .in contact with 5 the Vmolding means, the molding means wil1tend to make the string more round, smooth and compact.. It is especially effective to this end where the various separate fine ribbons are kept` in approximately' proper relationship prior to the molding .by supporting and stretching the skeinina liquid bath. Since the molding means is'moved along the rentire length of the string,- it willalso tend to -insure uniformity of cross sectionfof the string.`

The invention alsov contemplates, in its preferred form, a series of partitions between the twisting skeins'to prevent interference between them. This permits putting theskeins closer together so as to mount more in a tank of convenient width. i

Additional advantages andiobj'ects oftheinvention will become apparent `from the following description and from the drawings,- in which:

Fig. .1 is a plan View of one form of the apparatus chosen for illustrationof this invention. Fig. 2 is a vertical longitudinal section on an enlarged scale of the structure s hown in Fig. 1.

Fig.'3 is a transverse vertical section taken approximately on the line 3-3 of Fig. 2.

' Fig. 4 is a corresponding view taken on the line Fig. 5 is a fragmentary perspective View of the mold shown in Figs. 1, 2 and3.

j Fig. 6 isa vertical transverse `cross sect-ion quality of the nished strings.' `The present `inshowing a simplied form of "the invention in which the molding f means is moved alongthe length of the string-by hand.

Y Fig. 'Il is a fragmentary longitudinal cross section taken`l4 approximately on the line 1--1 of Fig. 6, showing one cross sectional shape `of the simplified molding means. .Y v f f Figs. 8 andA 9 are fragmentary sectional and k plan views, respective'1y,.of another modification .of the invention.

Fig. 10. is La fragmentary view correspondingt'o part of Fig. 8 but showing `the partitionsresting on the mold plates before. thelatter 4start to move. i i y Although the Ainventionfisdescribed in` detail hereafter,.as required by R.. S. 4888the claims Y are `not' tobe unnecessarily. limited by. the detailed disclosure,- since rthe invention .may take many forms.

. Although three forms of the invention have been illustrated, they have-al1 been illustrated in .conjunction with a string. twisting apparatus such as was describediripmygprior Patent No.

2,104,730. In.this.apparatus,"a tankl is provided which'holdsfa. Ibathvofwater'zwhich suspendswthe strings while they ,are being twisted.

At one end of the tank are provided a plurality of. rotary spindleszI I,.whleitoward-.the other end of this tank, non-rotary spindles l2 are provided.

yEach of thespindles bears a hook I 3.to which vloops I4 may be hoioked. Each loop I4 is formed by a cord `with which a plurality of very fine ribbons. of ,gut are secured together ,to form the `skein or hank I5 to b etwislted. Although-the spindles 'could be located'below the surface Iii of the water, the spindles I2, at least, are prefer.- ably located just above the surface so that with `only aislight amount of; droop, the skeins Will be `suspended in or-iloated 0 11` the water. The nonrotatine spindlesvv I Zmay; conveniently be provided withfdownwardextensions t0 hold their jends of the skeins at orbelow the surface. In Aorder to 4apply tension to the skeinsnduringthe twisting operation, the non-rotary spindles I2 45v from the rotary spindle. Igntheillustrated form, yeachis independently slidable in a bracket Il are mounted for translation or sliding toand 20. A-cord 22 is secured 1to each ofthespindles 12, extends over a pulley and, is drawn taut by a weight 25. The-bar I1 is initially positioned so that it is closetethe collar 20 Closest tothe string I5, so that as the string is shortened by twisting thereof, the spindle I2 may slide in the bar I1 as far as may be necessary to maintain an even tension on the string I5.

The rotary spindles I I. are held against lengthwise movement by collars 29. Each of the spindles II is equipped with a worm gear 3U meshing with a worm shaft 3| driven by a motor 32 through suitable gearing 33. A counting switch, indicated diagrammatically at 34, which may initially be closed by the switch lever 35, serves to stop the motor after a selectednumber of rotations of the worm gear 30 so as to give the strings l5 the exact number of twists desired. The number will, of course, vary with the length of the string and could be varied on account of other conditions such as the size of the string and size or number of the ribbons:y Roughly speaking, '75 turns per inch of the string is good practice. The strings, or skeins, are made up in llengths from 2 to 20k feet, or more, according to the use to which they'are to'be put.

Water is supplied through the inlet pipe 35 and the level of the water is controlled byoutlet pipe 31. Since the waterV and the gut are of approximately the same density, the gutwill either float or substantially float in the water so that, except for centrifugal force as it is twisted, it will act as 'if it were weightless. If one ribbon of the gut happens to be heavier than the others,

or slightly longer, it will not sag below the ,others priorto twisting. This is -very desirable because if one' ribbon sags below the other prior to. twisting, it is likely to be wound on the outside of Vthe others instead of being twisted in amongthem.

According to thepresent invention, the Aapparatus-thus far described is improved by the addition offlongitudinally movable molding means. In the vfor-m shown in Figs. 1-5, this molding means comprises a carriage 4I which is carried by and may be driven longitudinally by screws 42,.. The carriage may comprise transverse base plates 43 and 44 to which may be secured brackets r46. Each bracket is secured toand restslon 'a threaded block.r41rwhich rests onrone of: 'the screws 42. The base plates 43 and 44 lie below the skeins I and vmay lie at or slightly below the. surface'4 of -the water. Above the base -plate 43 is positioned a holder plate v48 .which coacts with the plate 43 to yieldably hold. the various skeins I5 so as toltend to'conne the twisting of the skeins to Vthat. portion of the l plate. "These molding-plates 4,4 and 49 engage the skein within the'z'one ofI the twisting action. It may make very little difference whether any of the twisting action takes place to Vthe!v left of the plate 44 asseen in Fig. 2, orwhether it mainly takes place above the plate 44. vIt is evident, however, that the gripping action of molding plates-44 and 49 will sufiiciently oppose the twisting of the skeins I5 sov that not, all of the twisting action will occur to -thelleft of the 'mold plate 44 and, hence, at least -some Vof it will `occur above'the ymoldplate 44.y Expressed diiferently, the Vspeed of the movementof carriage 4I with respect to the speed of the rotation of spindle II should be such that a major portion of the twisting action takes place above the mold 44 and so that the twisting is nearly complete in that portion of the skein or string which is to the right of the molding plate 44. Furthermore, the twisting in the portion of the skein to the left of plate 44 should not be tight enough to prevent readjustment of the various ribbons of one skein with respect to one another. If the skein is to be twisted '75A turns per inch, the carriage may be moved approximately an inch for each 75 turns. It is thus apparent that during the twisting of the skein, that portion in which the twisting action is taking place is at the time of the twisting action rotating in contact with the molding plates 44 and 49 so that the projection of any ribbon beyond the others ,is substantially prevented. In short, the moldpolishing l,will still bedesired anda slight amount of sanding may often also be desirable, the

karnountof sanding necessary is greatly reduced.

Furthermore, the strengthof the finished string is increased'as there isno danger that anyone ribbon will project far enough from the other ribbons to have a major portionof its cross section sanded away. The invention, furthermore, produces greater uniformity in the cross; section of the finished string since there is no danger `of excessive irregularity of contour at some points which will require excessive. sanding' at those points, while at other points only slight sanding willbe necessary. In short, the twisting apparatus and method of this invention produce such a smooth surfaced and roundstring that only a minimum of abrasion is required throughout the length of the string. It should be observed, fur- .thermor`e,thatr even when irregularities appear in the ribbonsthe molding 4plates 44 and 49 Will tend to mold out these irregularities.

It is .preferred that the molding plates 44 and 49 be provided Vwith a plurality of notches 5I, those on lthe plate "44 opening upwardly and those on theplate 49 opening downwardly. The sides of thesenotches preferably diverge as shown to facilitatethe position of the skeins therein to tend to reduce the skeins to a minimum diameter. Furthermore, the notches 5I may be tapered from end to end, or rather from the lefthand'edge `of molding'plate 44 to the right-hand edge of molding plate 44 with the smaller end at the right so that there will be'a tendencyA to com- .press the skein more and more tightly as it is -twisted. Of course.' all of the edges of the vari- A ous plates 43, 44, 48 and 49 may be rounded off so that no sharp edges Will engage the gut.l vThe -p1ates are preferably all made of or plated with a place, being. maintained in position in anyfsuit-y able manner, as by pins 52. The tension-of the respective spacing of the top p1ates143 and 49 'from the base plates may be preferably adjusted by hand screws 53 vthreaded vonV pins )52..- These plates may be suitably braced to preventtheir bowing.4 It may be mostconvenient. to havexthe pins 52 plvoted'v to lugs. 54 and to have the ends*V Ywhich the hand screws 513i may beturned to providethe desired' spacing.

The counting switch34. is'set` for'Y theV desired ynumber of revolutions, and the switch lever 35 is thrown -to` :start the-motor 32.-- This` rotates the spindles H and .the screws yi2 so that the skeins 'are twisted `and simultaneouslythe'carriage 4l is `moved longitudinally ofthe tank l0'. When the carriage 4I reaches the limit .ofiits movement and the skeins have reached the proper twisted condition. simultaneously, .the counter switch 34'cooperatesfto turn off the motor 32. Oi course, if desired, thefcarri'age` "lllY could ride onto lthe unthreaded portion of the `screws'42 at the end of their movementgand the twisting ofthe skeins could be continued alittle longer. After twisting ofthe skeins is completed, the skeins are removed from the hooks I3 and the carriage is elevated from the screws 42, this being made possible by virtue of the fact that: the blocks 41 extend only half way around the screws 42. Thus, it is not necessary lto rotate the screws 42 in a reverse direction to return the carriage 4'I to the `starting position, but, Vas previously stated, thecarriage lil, or rather the base plates 42. and @3, may be set on the screws 42 at the desired position.

Although' it is desirable tov have the weight of the plates rest at least partially on the screws ft2 so' as to keep the threads ofthe screws 42 and the threads of blocks 41 in suiflciently flrm en;

gagement, it willbe'observed that the brackets dii lie close to the upper edges of the tank lll' so that ii the screws 42V wouldrotherwiseV sag too much under the weight of the plates, partof the weight of the plates will be supported by the tank iii. Gf course, if desired, the screws 42 could be supported at a plurality of intermediate points as indicated at 56 so as not to sag appreciably since such supporting is made possible by virtue of the fact that the blocks 41 extend vonly half way around the screws 42.` n y.

In Figs. dandy?, a simplified form 0f the inventionv has Vbeen shown in which the carriage 4l! slides alongthe upperedges or flanges 56-of the tank l@ and is moved manually. In this form, a further simplification has also been shownin that the molding plates 44 and4 are smoothsurfaced instead of being provided with ,the

notches l.' In short, they may be of the same nature as the elanfiping plates 43 Yand 48`. The

clamp-ing plates 43 and 43 may be provided. with screw adjustment, as shown in Fig. 4, or may reiy simply on the weight of the upper plate '48.

carriage along the tank, and pressing on theVV is required for` judging the best speed ofmovement of the carriage `by watching the twisting. of

the skein.` .Y

For further simplification, it has been found that the clamps 43 and 43 maybe omittedgfand in fact, the manual control carriage comprising merely the plates `44. vand figg" has been found in actual experience to be very satisfactory.

Figs. 8, to 10 illustrate an additional .feature 'of the invention that may be combined with yany of the formsillustrated in the other iigures. According to this `feature of the invention, a partition plate 6l is positioned duringthe twisting operation between each pair of adjacent skeins. These partitionplates may conveniently al1 be secured to a` hinge plate 62 hinged by Va pin 63 to the tank It. The partition plates 6I may be braced at their` outer endsand held at theY right depth during the twisting operation by an'angle bar 64fwhich may rest on the sides of the tank l0.

These partition platesarevery advantageous in preventing the tied ends ofthe skein from rubbingv ,against one another as they rotate. Heretolorel it has beennecessary` to space the skeins ratherwidely apart to prevent them from rubbing against each other. By the use ofthe partitions it is possible to mount them more closely together. It is believedy that they can bel spaced with one inch centers. This close spacing ofthe skeins will make it possible, to either vprovi-de more skeins in a tank of `a given width or use a narrower and hence cheaper and more convenient tank for a given number of skeins,

When the skeins have been completely twisted, the operator grasps the bar 64 and swingsfthc entire partition unit out of the way, as indicated by the dotted` lines in Fig.8. This renders the hooks i3 as easily accessible as if the partitions were not provided. After removing the twisted skeins and attaching fresh skeins,y the molding plates 44, etc., ,may be moved to the ystarting position and the partition plates swung down onto the molding plate 49, as seen in Fig. 9. A dependingv portion E6 of each partition plate 6l will in this position extend down between Vthe tied ends ing plates are moved along the skein,either man-` ually orby screws 42, they will gradually pass out from under thepartition plates 6| and let these plates drop to theposition shown in Fig. 8, injwhich they will separate the twisting skeins a little more thoroughly-than if they were retained in the position shown in Fig. 10. Of course, if it were desired, the molding plates could be slotted fromthe `right-hand end, so as to let the'partition plates fall tc their final positions earlier or even initially. A`Likewise, the molding plates Ycould be corrugated so `as to provide deep grooves between the skeins into which the partition plates could nthis event the partition `plates could extend the full length of the vat so as to avoid any difficulty from a broken strand in a skein.

Theknotted end of the twine loop onto which the ends of the ribbons comprising each skein are looped forms a bulky ball, sometimesexceeding a half inch in diameter. Out of this ball eX- tend` the tail ends of the ribbons, which, if not cut off very carefully, will ily around during the spinning. These balls and their tails of gut are necessarily side by side, and it is this point where the units contact each other, cause snarling, breakage, and serious tangling. Untangling one of these snarls often takes more time than aitotal loading, spinning,- and. unloading operation.V `The partitions practicallyk eliminate this trouble, and therefore are really very valuable.

From the foregoing, it is seen that an apparatus and a method have been providedfor producinggut strings more eiciently, more economically, and with greater perfection, particularly by molding `the string while the skein is being twisted, Aso that none of the ribbons making up the skein is' permitted to extend beyond the circular contour of the string and so that the skein will be shaped to a uniform round contour requiring! a minimum of sanding and polishing throughout itslength, f Y ItV should be recognized that, although the molding features of this invention are preferably used together with the feature of suspending the skeins in water` during twisting, they may be used without the water suspension, if desired.

I claim: f .v Y 1 e `1. The process of making gut string which includes twisting a skein of gut ribbons `of substantially uniform length in a bath of liquid while applying tension-to the skein, and While yieldably applying a molding pressure to a prtion of the skein-where twisting action is taking place gand which has not yet been twisted too tightly to permit readjustment of the ribbons with respect to one another.

2.l The process of making gut string which includes stretching Va skein of gut ribbons, Vpartially supporting the skein with a bath'of liquid to prevent the sagging of some Yribbons below others, twisting the skein and while twisting it applying a molding pressure-to a side of the portion thereof being twisted, and readjusting the ribbons of the skein with respectto one another to provide an approximately round contour.

3. The process of making gut string which includes stretching a skein of gut ribbons, partially supporting the skein intermediate its ends to prevent the sagging-of some ribbons below others, twisting the skein and while twisting it applying a molding pressure to a side of the portion thereof being twisted, and readjusting the ribbons of the skein with respect to one another to provide anapproximately round contour.

4. The process of making -gut string which inc'ludes stretching a skein of gut ribbons, twisting one end of the skein while restraining the other end from twisting, applying av molding pressure lirst near the twisted end of the skein to mold the portion of the skein being twisted and shifting the point of application of pressure from adjacent the twistedV end of theV skein to the stationary end of the skein as the twisting action progresses from one end of the skein to the other.

5. In apparatus of the class described, a bath, spaced spindles adapted to hold the skein in the bath, means to .tension the skein, means torrotate one of the spindles, and molding means for yieldingly applying a molding pressure to a portion of the skein being twisted by the rotation of the spindle. Y

6. In apparatus ofthe class described, a bath, spaced spindles adapted to hold the skein in the bath, means to tension the skein, means to rotate one of the spindles, molding means for applying a moldingk pressure to a portion, of the skein being twisted by the rotation of the spindle, and means for moving the molding means longitudinally of the skein.

7. In `apparatus of the class described, abath, spaced spindles adapted to hold the skein in the bath, means to tension the skein, means to rotate one of thespndles, molding means for CIK applying afmolding pressure to a portionfofthe 'skein ybeing twisted by the rotation of the spindle,

and automatic means operating in timed'relation with the rotating spindle for movingthe molding means longitudinally of the skein.

8. In apparatus of the class described, a bath, spaced spindles adapted to.hold the skein in the bath, means to tension the skein, means to rotate one of the spindles, and molding means forV applying a molding pressure to a portion of the skein being twisted by the rotation of the spindle; said molding means including substantially.A rigid means adapted .to yieldingly engage opposite sides of a skein. v

9. In apparatus of the class described, a bath, spaced spindles adapted to hold the skein in the 'bath means to tension the skein', means to rotate one of the spindles, and molding means for applying a molding pressure to a portion of the skein being twisted bythe rotation of the spindle; said molding means including substantially rigid means adapted to engage opposite sides ,of a skein at points staggered longitudinally of the skein.

10. In apparatus of the class described, a bath, spaced spindles adapted to hold the skein in the bath, means to tension the skein, means to rotate one of the spindles, andmolding means for applying a.molding pressure to a portion of the skein being twisted by the rotation of the spindle; said molding means including substantially rigid means adapted to engage opposite sides of a skein atpoints staggered longitudinally of the skein and additional means slidably clamping the skein and positioned beyond the molding means from the rotating spindle.

11. In apparatus of the class described, means for rotating one end of each of a plurality of side-by-side skeins to twist the skeins, molding meansfor applying a molding pressure simultaneously and jointlyA to each of the skeins being twisted, and means for moving the molding means lengthwise along the skeins.

l2. In apparatus of the class described, means A'for rotating one end of a skein, and molding means adapted to be moved along the skein from the rotating end and-constructed for `applying a frictlonal pressure to the skein effective at one time along a4 substantial length thereof whereby twisting action takes place within the zone of the 14. In apparatus of the class described, spaced i spindles adapted to hold the skein, means to tension the skein, means to rotate vone of the spindles, molding means for applying a molding pressure to a portion of the skein being twisted by a .rotation of the spindle, and means for moving the molding means longitudinally of the skein.A

1 5. In apparatus of the class described, spaced spindles adapted to hold the skein, means to tension the skein, means to rotate one of the spindles, molding means for applying a molding pressure to a portion of the skein` being twisted by the rotationof the spindle, and automatic means operating in timed relation with the rotating spindle for moving the moldingv means longitudinally of the skein. l

16. In apparatus of the class described, a spindie adapted to hold the skein under tension,

means to rotate the spindle, molding means for applying a mold-ing pressure to a portion of the rality of spindles in substantially side-by-side relationship each adapted to hold a skein under skein being twisted by the rotation of the spinmeans for applying a molding pressure to a portion of each skein being twisted by the rotation of the spindle, automatic means operating in timed relation with the rotating spindle for moving the molding means longitudinally of the skein, and a partition plate resting on the 'molding means in the j starting position `thereof and extending between the ends of the rotating skeins and movable, after the molding means has moved, to a position between additional portions of the skeins and biased toward said position whereby it will ,automatically move to said position as the molding means moves. Y

18. In apparatus of the class'described, a plurality of spindles in substantially side-by-side relationship each adapted to hold a skein under tension, means to rotate each Spindle, molding means for applying a molding pressure to a portion of each skein being twisted by the rotation of the spindle, means for moving the molding means longitudinally of the skein, and a partition plate resting on the molding means in the starting position thereof and extending between the ends of the rotatingskeins and movable, after the molding means has moved, to a position between additional portions of the skeins and biased toward said position whereby it will automatically move to saidv position as the molding means moves.

19. In apparatus for making gut string, a plu- `attaching the skeins to the spindles.

21. In apparatus of the 4class described, a plutension, means to rotate each spindle, molding Vmeans for applying a molding pressure to a portion of each skein being twisted by the rotation of the spindle, means for moving` the molding means longitudinally of the skein, and a partition plate resting on the molding means in the starty ing position thereof and movable, after the molding means has moved, to a position between the skeins and biased toward said position whereby it will `automatically move to said position as the molding means moves.

22. In apparatus of the class described, a plurality of spindles 4in substantially side-byside` relationship each adapted to hold a `skein'under tension, means to rotate each spindle, molding means for applying a molding pressure to a portion of each skein being twisted by the rotation of the spindle, means for moving the moldingV means longitudinally of the skein, and a partition plate extending between the ends of the rotating skeins.

23. Apparatus for making gut strings having a plurality of spindles in substantially side-by-side relationship, and means for rotating each spindle, and in which a skein is attached to each spindle by means which leaves the end of the skein loose,

characterized by a partition plate extending between the loose ends of the skeins as they are rotated by the spindles.

24. Apparatus for making gut strings having a plurality of spindles in substantially side-byside relationship, and means for rotatingeach spindle,

- and in which a skein is attached to each spindle by means which permits the end portion of the skein to gyrate dueto centrifugal force as the spindle is rotated, characterized by `a partition K spindles adapted to hold the skein, means to tension the skein, means to rotate one of the gspindles, molding means for applying a molding pressure to a portion of the skein being twisted by the rotation of the spindle, and automatic means operating in timed relation with the rotating'spindle for moving the molding means longitudinally of the skeincomprising a pair of generally horizontal screws extending generally parallel ofthe skeins and driven in timed relation to the spindles, a threaded block engaging the y the lower portion of the screw exposed, and support means for the screw at a position intermediate its ends engaging the lower exposed portion of the screw for supporting the same.

CARL G. BJORKMAN. 

